Sunday, May 13, 2012

Veterinary Vision

During the month of May, Veterinary Vision in San Carlos gives free eye exams to certified service dogs. While on this assignment, I was introduced to another worthy organization, Paws For Purple Hearts, whose goal is to help veterans learn to train service dogs. Three golden retrievers, all litter mates, were being trained at PFPH for a lifetime deployment as service dogs for three disabled vets.

In preparation for the assignment, I left my 70-200 lens behind (after all, the office couldn't be THAT big), and instead carried a 60mm macro and an 85mm 1.8. I wanted a shallow depth of field for the shot, and since I would be shooting in low light, felt the speed would come in handy.

Here Eldridge, Elaine, and Ethan wait patiently while PFPH instructor Sandra Carson finishes the necessary paperwork. I chose the day when all three dogs would be getting their exams. This way I would have three chances at making a decent photograph. Having discussed the procedure with Dr. Albert Mughannam, the veterinarian who would be performing the exam, I decided to make my shots from over the Doctor's shoulder and concentrate on the dog's eyes. I had given the shot considerable thought, and knew that I would need to include some dog features to help the photo along. I was hoping to include an upright ear or a snout in the photo to add some context.

With the first dog in place and with Dr. Mughannam in position, I was ready. I had my 60mm macro mounted on my D300. As soon as the lights went out, I knew I was in trouble. I had assumed that the fluorescent lighting would be on during the examination, but to examine the retina, you must dilate the pupil. Obviously, the simplest way was to dim the lights. I scrambled to adjust my exposure to the proper level. Also, the small spotlight that Dr. Mughannam used was probably close to an incandescent light source, so my initial florescent white balance setting was now way off. Rather than guess, I decided to run with it and hope that I could correct it in post production. I adjusted the camera to 1/100 second, F 2.8, ISO 800, and took a shot. There were some "blinkies" but not some much as to be unrecoverable when processed in RAW. I held my breath and started shooting. This first burst was a little busy, and a bit too menacing. I also wasn't getting the visual impact I was hoping for.

Now for the right eye. I decided to go with a faster lens to gain back one stop of light, so I changed to the 85mm 1.8, I re-set the shutter to 1/80, and shot at F 2.0, The ISO remained at 800.

In this burst, the last three photos are very close to what I had in mind. In fact, the are better in some ways because the dog's nose is clearly visible, and the the direction of the dog's gaze pull the photo together. Again, the background looked a little "busy" and might detract from the image. I noticed that the placement of the light was critical, since the eye was clearly visible only in the last shots.

The examination went very quickly, and before I knew it, all three were done. In desperation, I asked Dr. Mughannam to re-examine Elaine, the last dog, after making some specific requests. First, the large magnifying was held at the top of the image, above the dog's forehead, until it was needed. I also had the the magnifying glass turned slightly to show off its round contour. Finally, I asked that the examination light be held away from the dog's eye until I gave the signal. When I was ready, we started shooting.

While trying to maintain critical focus on the eye itself, some visual elements slipped in and out of the frame, specifically Ms. Carson's right thumb. It appears in full only in the first two sample images. In subsequent shots, she moved her hand lower on the dog's snout, cutting off the tip. Only the first two shots had the complete thumb and were therefore kept in the running, but only one of them is properly focused.

In retrospect, this was shooting at its fastest. The camera was not set to fire continuously because I wanted the option to determine, as closely as I could, the exact moment the exposure was to be made, human reflexes and mechanical delays notwithstanding. In all, 28 frames were taken in about two minutes, each one being the best combination of composition and timing I could make. There wasn't time to "chimp" between shots and there were a few dog-blinks and off-centered highlights. Looking back, the 85mm lens might have been a bit too long for the job. But the wide aperture gave me exactly what I wanted, so far as the eye was concerned.

Here is the final image, right out of the camera. The incandescent light source in the florescent enviornment of the examination room gave the shot a yellow glow which I neutralized in post production by removing the color cast. I liked the way the two hands surround the eye, and the way the highlight in the magnifier is aligned diagonally with the dog's eye and the corner of the photo.

I think there is a yin/yang simplicity to the photo. The reflection in the magnifying glass is actually an inverted image of the dog's head, and based on the alignment, draws the viewer's eyes directly to the dog's. I like the image for its simplicity, a sentiment shared by many who saw it.